Increment version to 2.19.0-SNAPSHOT

Signed-off-by: opensearch-ci-bot <[email protected]>

Author: opensearch-ci-bot

build.gradle

@@ -10,7 +10,7 @@ import org.opensearch.gradle.testclusters.StandaloneRestIntegTestTask
 buildscript {
     ext {
         isSnapshot = "true" == System.getProperty("build.snapshot", "true")
-        opensearch_version = System.getProperty("opensearch.version", "2.18.0-SNAPSHOT")
+        opensearch_version = System.getProperty("opensearch.version", "2.19.0-SNAPSHOT")
         buildVersionQualifier = System.getProperty("build.version_qualifier", "")
         version_tokens = opensearch_version.tokenize('-')
         opensearch_build = version_tokens[0] + '.0'